Among the most ubiquitous effects of addictive drugs, but the least well studied, is drug craving. There has not even existed a validated psychometric instrument for the evaluation of craving that would lend itself to the systematic development of medications for treating drug craving. We have recently developed such instrumentation for cocaine, heroin, alcohol, and marijuana. This research should help us to identify mechanisms of addiction that are common across drug classes and therefore lead to a better understanding of the mechanisms that underlie the drug cravings. Our initial findings indicated that craving for cocaine and heroin is a multidimensional construct, involving an admixture of urges and desire, intent to use, loss of control over use, and anticipation of positive outcome. Subject testing has been completed with the newly developed Alcohol Craving Questionnaire and Marijuana Craving Questionnaire. Finally, to extend the generality of the research and investigate ethnic and cultural factors, a Standard Spanish version of the Cocaine Craving Questionnaires and Manual has also been developed. Recently, we have using the Questionnaire on Smoking Urges to measure the manipulation of tobacco craving in the laboratory. Using narrative scripts that either contain explicit descriptors of smoking urges or scripts that contain no urge descriptors, we have shown that tobacco craving can be manipulated in a drug-abusing population and that craving can vary along a continuum. Craving is also associated with negative mood states. We intend to investigate the effect of tobacco craving on the cognitive deficits seen during nicotine withdrawal. We have also recently revised the Questionnaire on Smoking Urges to include items related to loss of control. Subject testing has begun to validate the revised questionnaire. These advances in instrument development and enhanced understanding of craving should enable more rapid progress in the ability to produce more selective and effective medications and other interventions to meet the needs of those addicted to drugs. With these instruments we should be able to predict which craving dimensions may be relieved by medications and which will require other intervention to enable the person to achieve and sustain drug abstinence.